url bar animations

gistfile1.swift

    private func updateLayoutForEditing(#editing: Bool) {


        self.progressBar.hidden = editing
        self.editTextField.hidden = !editing

        self.locationContainerConstraints.uninstall()

        if editing {
            self.locationContainer.snp_updateConstraints { make in
                self.locationContainerConstraints = make.leading.equalTo(self).offset(URLBarViewUX.LocationLeftPadding)
                make.trailing.equalTo(self.cancelButton.snp_leading)
                make.centerY.equalTo(self).offset(StatusBarHeight / 2)
            }
        } else {
            self.locationContainer.snp_updateConstraints { make in
                self.locationContainerConstraints = make.leading.equalTo(self).offset(URLBarViewUX.LocationLeftPadding)
                make.trailing.equalTo(self.tabsButton.snp_leading).offset(-10)
                make.centerY.equalTo(self).offset(StatusBarHeight / 2)
            }
        }

        // show both buttons during transition
        self.tabsButton.hidden = false
        self.cancelButton.hidden = false

        UIView.animateWithDuration(0.4, delay: 0.0, usingSpringWithDamping: 0.7, initialSpringVelocity: 0.0, options: nil, animations: { _ in
                if editing {
                    self.cancelButton.alpha = 1
                    self.cancelButton.transform = CGAffineTransformIdentity
                    self.tabsButton.transform = CGAffineTransformMakeTranslation(self.tabsButton.frame.width, 0)

                } else {
                    self.cancelButton.alpha = 0
                    self.tabsButton.transform = CGAffineTransformIdentity
                    self.cancelButton.transform = CGAffineTransformMakeTranslation(self.cancelButton.frame.width, 0)
                }

                self.layoutIfNeeded()
            }, completion: { _ in
                self.tabsButton.hidden = editing
                self.cancelButton.hidden = !editing
            })


    }